Needle placement manipulator with attachment for RF-coil

ABSTRACT

A needle placement manipulator includes, a needle holder configured to hold a needle, a guide system configured to position the needle holder to a predetermined direction with respect to a subject of needle placement, an attachment including an attaching portion to which the guide system is attached and a setting portion on which an RF-coil is set. A base surface of the setting portion is configured to be disposed on the subject.

BACKGROUND

Field

The disclosure of this application relates generally to medical devices,and in particular it relates to a needle placement manipulator and aneedle placement manipulator with attachment for RF-coil.

Related Art

The use of imaging modalities, such as ultrasound, mammography, computedtomography (CT), Magnetic Resonance Imaging (MRI) and the like, toassist in identifying and treating abnormalities within the body of apatient, has gained increased acceptance in the medical field. Theabove-named and other imaging modalities generally provide good contrastbetween different soft tissues of the body. Thus, many of thesetechniques are being used to depict the boundaries of damaged tissuewithin healthy tissue for accurate identification and treatment.Advanced diagnostic procedures, however, require further validation andrefinement in localization of damaged tissue. This further validationand advanced localization can be performed by needle biopsy procedures.To help define the boundaries of damaged tissue within healthy tissuewith greater accuracy, needle guidance systems have been proposed.

A non-patent literature article entitled “MRI Guided NeedleInsertion—Comparison of Four Techniques”, by Fisher et al., describesfour techniques for needle placement: 1) image overlay that projects anMR image and virtual needle guide on the patient, 2) biplane laser withneedle trajectory marked by intersecting transverse and oblique sagittallasers, 3) handheld protractor with pre-angled guide sleeve, and 4)freehand insertion. Conventionally, all of these techniques haverequired removing the patient out the imaging modality for needleinsertion.

In the medical environment, it is necessary to position a needle tipprecisely inside tissue or a specific organ for accurate diagnosis orminimal invasive therapy. Biopsy, ablation, cryotherapy, aspiration anddrug delivery are examples that require high precision needle placement.Prior to a percutaneous incision, a target area of interest (e.g.,tumor, nodule, etc.) is confirmed by means of non-invasive imaging withMRI, ultrasound or other imaging modality. Once the target area ofinterest is positively determined, the clinician decides an entry point,inserting direction and depth to be reached by the needle based onexperience. This process often requires a lengthy trial and errorroutine, which can be deleterious to the patient. Accordingly, in thelast few decades there has been an increased interest in the developmentof needle guiding systems that can improve accuracy of needlepositioning, minimize patient discomfort, and shorten time of operation.

In the realm of needle guiding systems having a handheld protractor withpre-angled guide sleeve, US Patent Application Publication 2011/0190787disclosed by Hirdesh Sahni (herein “Sahni”) is an example. Sahnidescribes an “IMAGE GUIDED WHOLE BODY STEREOTACTIC NEEDLE PLACEMENTDEVICE with FALLING ARC”. In Sahni's system, the device may becompatible with both CT and MRI modalities, but the patient has to holdthe breath while the needle is being passed into regions that move onrespiration. The device can be placed on the skin or on near an exposedorgan of a patient, but its function can be jeopardized by movement.

In the realm of modality-guided needle placement systems, US PatentApplication Publication 2006/0229641 disclosed by Rajiv Gupta et al.,(herein “Gupta”) is an example. Gupta describes a “GUIDANCE ANDINSERTION SYSTEM”, in which the insertion angle of the needle is guidedby two arc-shaped arms which are driven by motors respectively attachedat the axis of each arm. The device can be configured for use with animaging apparatus, such as CT scanner, to allow the device and tool tobe operated while viewing the device positioned in relation to a targetsurgical site. The device can be placed on a patient's skin and fastenedby belts. The device can passively compensate for patient's movement.

In MRI-guided percutaneous interventions, accurate needle placement isof great concern and of considerably more difficulty that in needleplacement systems for other modalities, such as CT or ultrasound. Unlikeother modalities, MRI makes use of the property of nuclear magneticresonance (NMR) to image nuclei of atoms inside the body. To that end,during an MRI scan, a patient is disposed within a powerful magnet wherea large magnetic field is used to align the magnetization of atomicnuclei in the patient's body, and a radio frequency (RF) pulse isapplied to alter the linear magnetization of the atomic nuclei. Thiscauses the atomic nuclei to absorb energy from tuned radiofrequencypulses, and emit radiofrequency signals as their excitation decays.These signals, which vary in intensity according to nuclear abundanceand molecular chemical environment, are converted into sets oftomographic (selected planes) images by using field gradients in themagnetic field, which in turn permits 3-dimensional (3D) localization ofthe point sources of the signals (or damaged tissue). More specifically,the detected signals are used to construct 2D or 3D MRI images of thescanned area of the body.

In an MRI-guided needle placement system, therefore, it is preferredthat the entire positioning system consists essentially of non-magneticmaterials such that there is no danger of impairing the homogeneity ofthe magnetic field within an examination volume. In addition, in orderto track spatial positioning of the needle with respect to the guidingsystem, it is necessary to provide a marking point, such as a MRmeasurable fiduciary mechanically rigidly connected to the guidingsystem. In this manner, the position of the manipulator itself can bedetermined via MR measurement. U.S. Pat. No. 6,185,445 to Knutteldiscloses and example of such system.

Shortcomings of conventional technology include: 1. When applying theneedle placement manipulator to MR-image guided intervention, themanipulator and an RF-coil must be placed without interference betweenwith each other. The manipulator needs to be configured to fit with theRF-coil. The manipulator should be placed on top of RF-coils, and itshould be removable so that a clinician's workspace for observations andinterventions will not be limited, and so that the clinician can observethe patient through the opening of the RF-coil. The number of steps withwhich the RF-coil and the manipulator are positioned on the patient (thesubject of the needle insertion) should be minimized to shorten theprocedure, for the convenience of the patient and the clinician. Theposition and orientation of the needle with respect to the subject ofneedle placement should be precisely repeatable. The needle placementmanipulator should be made of materials which do not interfere with themagnetic field of the MRI scanner.

SUMMARY

According to at least one embodiment of the present application, aneedle placement manipulator includes, a needle holder configured tohold a needle, a guide system configured to position the needle holderto a predetermined direction with respect to a subject of needleplacement, an attachment including an attaching portion to which theguide system is attached and a setting portion on which an RF-coil isset. A base surface of the setting portion is configured to be disposedon the subject.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a needle placement manipulator according to a firstembodiment;

FIGS. 2A and 2B illustrates cross-sectional views of the needleplacement manipulator according to the first embodiment. FIG. 2Cillustrates an angular relationship between the rotational axes ofrotary guides and a needle holder axis;

FIGS. 3A, 3B and 3C illustrate examples of needle insertion at a singlecrossing point with various angles of insertion;

FIGS. 4A and 4B illustrate a maximum angle of inclination 63 and optimalrotational space determined by the maximum angle of inclination 63;

FIGS. 5A and 5B are sectional views of a needle placement manipulatorequipped with a motorized actuator, according to a second embodiment;

FIG. 6A illustrates a detailed sectional view of the left side of FIG.5A. FIG. 6B illustrates a detailed sectional view of the left side ofFIG. 5A using optical fibers;

FIG. 7A illustrates an example of a motorized needle manipulatorincluding set screws for locking the rotational guides in a stoppedposition, according to a modification of the second embodiment. FIG. 7Billustrates an example of a motorized needle manipulator in which thebase body includes a sliding portion to adjust a height of the crossingpoint, according to a further modification of the second embodiment;

FIG. 8A illustrates a perspective view of needle manipulator attached toan RF-coil, according to third embodiment; FIG. 8B illustrates asectional cut along vertical plane H-H of the needle manipulatorattached to an RF-coil;

FIG. 9A illustrates a sectional view of the needle manipulator cut alonga vertical plane H-H, according to the third embodiment. FIG. 9Billustrates a detailed view of section A shown in FIG. 9A where a firstattachment 30 engages with a second attachment 31 on an outer surfacethereof. FIG. 9C illustrates a detailed view of section A shown in FIG.9A where a first attachment 30 engages with a second attachment 31 on aninner surface thereof;

FIGS. 10A, 10B and 10C illustrates an exemplary procedure for attachingand detaching a needle manipulator to an RF-coil with attachmentstherefor;

FIG. 11 illustrates a perspective view of the assembled needlemanipulator attached to the RF-coil with first and second attachmentsengaged to each other;

FIG. 12 illustrates a sectional view of a motorized needle manipulatorattached to an RF-coil, in accordance with the fourth embodiment; and

FIG. 13 illustrates a block diagram of an automated image-guided needlepositioning system which includes a needle manipulator.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings which are illustrations of embodiments in which the disclosedinvention may be practiced. It is to be understood, however, that thoseskilled in the art may develop other structural and functionalmodifications without departing from the novelty and scope of theinstant disclosure.

In referring to the description, specific details are set forth in orderto provide a thorough understanding of the examples disclosed. In otherinstances, well-known methods, procedures, components and circuits havenot been described in detail as not to unnecessarily lengthen thepresent disclosure. Some embodiments of the present invention may bepracticed on a computer system that includes, in general, one or aplurality of processors for processing information and instructions,random access (volatile) memory (RAM) for storing information andinstructions, read-only (non-volatile) memory (ROM) for storing staticinformation and instructions, a data storage device such as a magneticor optical disk and disk drive for storing information and instructions,an optional user output device such as a display device (e.g., amonitor) for displaying information to the computer user, an optionaluser input device including alphanumeric and function keys (e.g., akeyboard) for communicating information and command selections to theprocessor, and an optional user input device such as a cursor controldevice (e.g., a mouse) for communicating user input information andcommand selections to the processor.

As will be appreciated by those skilled in the art, the present examplesmay be embodied as a system, method or computer program product.Accordingly, some examples may take the form of an entirely hardwareembodiment, and entirely software embodiment (including firmware,resident software, micro-code, etc.) or an embodiment combining softwareand hardware aspects that may all generally be referred herein as a“circuit”, “module” or “system”. Further, some embodiments may take theform of a computer program product embodied in any tangible medium ofexpression having computer-usable program code stored therein. Forexample, some embodiments described below with reference to flowchartillustrations and/or block diagrams of methods, apparatus (systems) andcomputer program products can be implemented by computer programinstructions. The computer program instructions may be stored incomputer-readable media that can direct a computer or other programmabledata processing apparatus to function in a particular manner, such thatthe instructions stored in the computer-readable media constitute anarticle of manufacture including instructions and processes whichimplement the function/act/step specified in the flowchart and/or blockdiagram.

It should be understood that if an element or part is referred herein asbeing “on”, “against”, “connected to”, or “coupled to” another elementor part, then it can be directly on, against, connected or coupled tothe other element or part, or intervening elements or parts may bepresent. In contrast, if an element is referred to as being “directlyon”, “directly connected to”, or “directly coupled to” another elementor part, then there are no intervening elements or parts present. Whenused, term “and/or”, includes any and all combinations of one or more ofthe associated listed items, if so provided.

Spatially relative terms, such as “under” “beneath”, “below”, “lower”,“above”, “upper”, “proximal”, “distal”, and the like, may be used hereinfor ease of description and/or illustration to describe one element orfeature's relationship to another element(s) or feature(s) asillustrated in the various figures. It should be understood, however,that the spatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, a relative spatial term such as “below” can encompassboth an orientation of above and below. The device may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein are to be interpreted accordingly.Similarly, the relative spatial terms “proximal” and “distal” may alsobe interchangeable, where applicable.

The terms first, second, third, etc. may be used herein to describevarious elements, components, regions, parts and/or sections. It shouldbe understood that these elements, components, regions, parts and/orsections should not be limited by these terms. These terms have beenused only to distinguish one element, component, region, part, orsection from another region, part, or section. Thus, a first element,component, region, part, or section discussed below could be termed asecond element, component, region, part, or section without departingfrom the teachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a”, “an”, and “the”, are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It shouldbe further understood that the terms “includes” and/or “including”, whenused in the present specification, specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groups thereofnot explicitly stated.

In describing example embodiments illustrated in the drawings, specificterminology is employed for the sake of clarity. However, the disclosureof this patent specification is not intended to be limited to thespecific terminology so selected and it is to be understood that eachspecific element includes all technical equivalents that operate in asimilar manner.

Exemplary embodiments will be described below with reference to theseveral drawings, where like reference numerals refer to like parts.

<First Embodiment>

The first embodiment of the present invention is directed to a solutionfor the issues mentioned above. FIG. 1 is a perspective view of a needleplacement manipulator 100 in accordance with the first embodiment. FIGS.2A and 2B are sectional views of the needle placement manipulator atdifferent operating positions.

As illustrated in FIG. 1, according to the first embodiment, a needleplacement manipulator 100 includes two circular ring-shaped rotaryguides (hereinafter referred simply to as “rotary guides”), which arearranged in a slanted orientation with respect to each other atop a basebody 5. Specifically, a first rotary guide 1 and a second rotary guide 3are arranged in a slanted orientation with respect to each other. Thetwo rotary guides 1 and 3 are supported by a base body 5. The base body5 is preferably a non-magnetic structure configured to be mounted on apatient's skin 8. As discussed in more detail below, the base body 5 andcertain other elements can be manufactured of disposable and recyclablematerials, such as plastics and/or composites thereof. The first rotaryguide 1 is supported by the base body 5 and connects to a first rotationbody 2. The second rotary guide 3 is supported by the first rotationbody 2 and connects to a second rotation body 4. The second rotationbody 4 is configured to support a needle holder 6. The needle holder 6has a thru hole 6 b configured to guide a needle 7 therethrough. Theneedle holder 6 constrains the needle 7 to align to selected anglegeometrically determined by rotation of the two rotary guides 1 and 3.

The first rotation body 2 in this embodiment consists of three pillars 2a, 2 b and 2 c. But it is not limited to this structure. The firstrotation body 2 can be formed of other structures, for example, onepillar or plurality of pillars, or a shell structure or a shellstructure with holes. Many other shapes and structures may be readilyavailable to a person having ordinary skill in the art. Notably,however, when the rotation body 2 consists of one or at most threepillars, as illustrated in FIG. 1, an ample opening for viewing anincision point is advantageously provided. Similarly, the secondrotation body 4 consists of one or more pillars connecting the needleholder 7 to the second rotary guide 3.

Each of the rotary guides 1 and 3 respectively includes a set ofrotational devices 13 and 23, and a fixing element 1 b and 3 b.Rotational devices promote easy rotation of the rotary guides to adesired position; and the fixing elements hold the rotary guides fixedin the desired position to prevent movement during a needle incisionoperation. In this embodiment, fixing elements 1 b and 3 b are setscrews, and the rotational devices 13 and 23 are mechanical bearings. Inpreparation for an incision operation, a clinician or an automatedactuator manipulates at least one the two rotary guides (the guides canoperate independently from each other) to rotate the needle holder 6 toa predetermined angle. Once the desired position is reached, the rotaryguides are fixed by tightening the fixing elements (screws) 1 b and 3 b,so that the needle holder 6 is directed to a desired angle to reach atarget tissue 8 a under the patient's skin 8. In this embodiment, fixingmeans are set screws. Air-clutches also can be used as fixing meansinstead of screws. The air clutch is rotation-free when air-pressure issupplied from an air-supply source like a compressed gas cylinder or amedical air supply outlet in the surgical room; and when the air-supplyis shut, the air-clutch holds the rotation of the rotary guides fixed.

Referring back to FIG. 1, markers 10 a, 10 b, 10 c, 10 d, 10 e, 10 f, 10g and 10 h are MRI-visible fiducial markers which are arranged atpredetermined locations on the base body 5, and first rotary guide 1,and the second rotary guide 3. During an MRI-guided intervention, imagesof these markers are acquired by MRI-scanner to obtain the spatialposition and posture of each of these parts. Slits 5 a and 5 b providedwithin the base body 5 are slits for a belt to fasten the manipulator topatient's body.

In this embodiment in FIG. 1, the base body 5 is fixed to patient's bodyby fastening belts. But fastening is not limited to the belts only. Themanipulator can be fastened to a patient's body by bolts passing throughslits 5 a and 5 b to be fixed to bone of patients, or adhered to thepatient by adhesive tapes, suction cups, and so on. It is also can befixed to patient's bed or floor by a passive arm which can hold itsjoints by air clutch.

As illustrated in FIG. 2A, the first rotary guide 1 rotates around afixed rotational axis 1 a. And the second rotary guide 3 rotates arounda fixed rotational axis 3 a. The term “fixed rotational axis”, as usedherein, means that the axis of rotation is fixed with respect to itscorresponding rotating part. The needle holder 6 includes the thru-hole6 b through which a needle holder axis 6 a passes longitudinally. Theaxis 1 a of first rotary guide 1, the axis 3 a of second rotary guide 3,and the axis 6 a of the needle holder 6 are arranged to always cross ata single crossing point 9 located at the center of gravity of the basebody 5. As used herein, the term “center of gravity” refers to the pointat which all the surrounding weight is equal. That is, it is the pointat which an object is in balance.

In operation, the direction of the needle is determined by two angles ofthe rotary guides 1 and 3 without changing the crossing point 9. In FIG.2A, the needle holder axis 6 a is substantially perpendicular to thebase body 5, and thus also substantially perpendicular to the firstrotary guide 1. It can be said therefore, that at a given first positionthe needle holder axis 6 a can be made substantially perpendicular tothe first rotary guide 1. In this first position, the needle holder axis6 a can be made to substantially coincide with the axis 1 a. From thisgiven first position, the needle holder axis 6 a and consequentially theneedle holder 6 can be moved to any position between the initialperpendicular position (FIG. 2A) and a maximum inclined positionillustrated in FIG. 2B.

FIG. 2C illustrates the angular relationship between the rotational axis1 a of the first rotary guide 1, the rotational axis 3 a of the secondrotary guide 3 and the needle holder axis 6 a of the needle holder 6. Asillustrated in FIG. 2C, all of the axis 1 a, 3 a and 6 a coincide andare fixed at the crossing point 9. Here, it should be understood thatthe rotational axis 1 a of the first rotary guide 1 and the rotationalaxis 3 a of the second rotary guide 3 are preferably fixed with respectto each other. However, the needle holder axis 6 a of the needle holder6 is not fixed and can be moved around the axis 3 a and/or the axis 1 a.

In the position illustrated in FIGS. 2B and 2C, θ1 is the angle betweenthe rotational axis 1 a of the first rotary guide 1 and the rotationalaxis 3 a of the second rotary guide 3; and θ2 is the angle between therotational axis 3 a of the second rotary guide 3 and the needle holderaxis 6 a of the needle holder 6, when the needle holder axis 6 a is atits maximum inclined position. However, since the needle holder axis 6 acan be moved, the needle holder axis 6 a can be positioned at any anglebetween the first position (substantially perpendicular to the firstguide 1) and the maximum inclined position at a maximum inclinationangle θ3=θ1+θ2. The position of the needle holder 6 can be achieved bythe displacement of the needle holder axis 6 a around the axis 3 aand/or the axis 1 a of the rotary guides 3 and 1, respectively.

More specifically, as the second rotary guide 3 rotates around itsrotational axis 3 a, the needle holder axis 6 a is displaced (travels)around a cone formed by the inner diameter of second rotary guide 3 andthe crossing point 9. This cone will be referred to as a first cone ofacceptance. FIG. 3B illustrates a position where the needle holder axis6 a has been displaced to a predetermined position around thecircumference of the second rotary guide 3 from that shown in FIG. 2B.That is, as shown in FIG. 3B, the needle holder axis 6 a has beendisplaced around the first cone of acceptance.

Similarly, as the first rotary guide 1 rotates around its rotationalaxis 1 a, the axis 3 a of the second rotary guide 3 is displaced(precesses) around the axis 1 a. Since the axis 1 a and axis 3 a arefixed at the crossing point 9, the precession of axis 3 a around theaxis 1 a defines another cone, which will be referred to herein as a“second cone of acceptance”. The second cone of acceptance is formed bythe circumference defined by axis 3 a and the crossing point 9 withrespect to the axis 1 a, as the first rotary guide 1 rotates around itsaxis 1 a.

It should be recognized therefore, that needle placement can be effectedat the fixed crossing point 9 from anywhere within the first cone ofacceptance and/or the second cone of acceptance. FIGS. 3A, 3B and 3Cillustrate in explicit detail some examples of needle insertion atcrossing point 9 with various angles of insertion. In FIG. 3A, the firstcone of acceptance is formed when the second rotary guide 3 rotatesaround its own axis of rotation 3 a. In FIG. 4A, it is assumed that thefirst rotary guide 1 is fixed (does not rotate). In this assumed fixedposition of the rotary guide 1, the needle holder 6 can be displaced(rotated) to point around the base on the first cone of acceptance, butone point of the needle holder axis 6 a will be fixed at crossing point9. Now it is assumed that the second rotary guide 3 stops rotating.

Turning now to FIG. 3B, the second cone of acceptance is formed when thefirst rotary guide 1 rotates around its own axis of rotation 1 a. InFIG. 3B, it is assumed that that second rotary guide 3 is fixed (doesnot rotate). In the assumed fixed position of the second rotary guide 3,since the first rotary guide 1 is connected to the second rotary guide 3via the rotation body 2 (pillars 2 a-2 c), the needle holder 6 can bedisplaced (rotated) to any point around the base of the second cone ofacceptance, but the one point of the needle holder axis 6 a will stillremain fixed at crossing point 9. In this manner, the needle holder 6can be positioned at any angle between the perpendicular position andthe maximum inclined position.

FIG. 3C illustrates that both the first and second cones of acceptancecan be used to position the needle holder 6 at a desired position andangle, while still maintaining one point of the needle holder axis 6 aat the crossing point 9. More specifically, FIG. 3C illustrates thatboth the first rotary guide 1 and the second rotary guide 3 can berotated simultaneously (or separately) around their corresponding axis 1a and 3 a. In this manner, the second rotary guide 3 can rotate aroundits axis 3 a and can precess around the axis 1 a of the first rotaryguide 1.

Therefore, arranging the crossing point 9 at the desired needleinsertion point of the skin 8, allows a clinician to insert the needle 7from any angle within an acceptance cones allowed by rotation of therotary guides 1 and 3. In this manner, the target tissue 8 a can bereached from different incision angles without changing the position ofthe inserting point. In addition, since the needle may be inserted fromany angle within a cone of acceptance, with this manipulator a cliniciancan treat different regions of the tissue through only one insertionpoint on the patient's skin.

Referring now to FIGS. 4A and 4B a description is provided for a maximumangle of inclination θ3 and optimal use of rotational space determinedby the maximum angle of inclination θ3. As illustrated in FIG. 4A, theactual usable space within the cones of acceptance for the needle holder6 can be limited by the arrangement of the second rotary guide 3 in aslanted orientation with respect to the first rotary guide 1, above thebase body 5. In FIG. 4A, T indicates the approximate height from acontact surface, e.g., a patient's skin 8 to an upper surface of thefirst rotary guide 1 above the base of base body 5 (i.e., above theneedle incision point or crossing point 9); and R indicates the internalradius of the free space within the first rotary guide 1. Preferably,the point of needle incision or crossing point 9 is located at thegeometric center at the bottom of the first rotary guide 1. In additionto the height of the first rotary guide 1, the needle holder 6 attachedto the second rotary guide 3 occupies certain space above the base body5, and the needle holder 6 requires a minimum of inclination withrespect to the crossing point 9. When all of these parameters are takeninto consideration, it is estimated that the needle holder axis 3 a canhave an maximum inclination θ3 defined by equation (1), as follows:θ1+θ2≤θ3=π/2−tan⁻¹(T/R)  (1)

Equation (1) provides the condition when all 360 degrees (a completerotation) can be used for the second (tilted) rotary guide 3. However,to reach to the limit of equality of equation (1), the tilted secondrotary guide 3 may need to be larger than the first rotary guide 1and/or the tilted second rotary guide 3 may need to be positionedoutside of the horizontal first rotary guide 1. Accordingly, a person ofordinary skill in the art will understand the embodiments disclosedherein can be modified to have the second rotary guide 3 outside thefirst rotary guide 1 and yet maintain a maximum inclination angle θ3provided by equation (1).

Referring to FIG. 4B, it can be appreciated that the needle 7 extendingalong the needle holder axis 6 a will encounter a physical obstacle inthe horizontal first rotary guide 1. This limits the rotation of thesecond rotary guide 2 to a space [1] within a maximum allowable space[2]. Specifically, due to above-discussed actual size and arrangement ofthe rotary guides 1 and 2, as observed from a view direction A (shown inFIG. 4A), the maximum allowable usable space for maneuvering the needleholder 6 is an space [2] shown in FIG. 4B. However, the tilted secondrotary guide 3 needs not use the entirety of space [2]. Indeed, onlyhalf of space [2] can be used because whatever orientation of the needleholder 6 in that half-range of space [2] can also be oriented within theother half-range by using the rotation of the horizontal first rotaryguide 1. That is, rotating both the first rotation guide 1 and thesecond rotation guide 3 allows the positioning of the needle holder 6any part of the maximum allowable space [2]; this was alreadyillustrated in a more generalized manner in FIG. 3C.

<Second Embodiment>

FIGS. 5A and 5B are sectional views of a needle placement manipulator200, in accordance with a second embodiment. FIG. 6 is a detailedsectional view of the left side of FIG. 5A. The second embodiment issubstantially similar to the first embodiment. One notable difference inthe needle placement manipulator 200, according to the secondembodiment, is that the manipulator 200 includes motorized actuators forthe rotation of first and second rotary guides 1 and 3.

Specifically, in this embodiment, the first rotary guide 1 now includesa rotation drive unit 210, and the second rotary guide 2 includes arotation drive unit 220. In the first rotary guide 1, the rotation driveunit 210 comprises a piezoelectric actuator 11, a rotary slider 12, aball-bearing 13, a screw part 14, a pressurized means 15, a firstelectric cable 16, a position sensor 17, a rotary scale 18, a secondelectric cable 19, and an external casing 1.1 and internal casing 1.2.

As shown in FIG. 6A, the piezoelectric actuator 11 comprises a vibratorbody 11 a and piezoelectric material 11 b. The piezoelectric material 11b is fixed to vibrator body 11 a with adhesive. The piezoelectricmaterial 11 b embeds a plurality of electrodes (not drawn) which applyelectric voltage to the piezoelectric material 11 b. Piezoelectricactuator 11 is supported through pressurized means 15 to internal casing1.2 of the rotary guide 1. External casing 1.1 and internal casing 1.2are relatively rotatable by bearing 13 which is fixed by the screw part14. The rotary slider 12 is fixed to external casing 1.1. Thepiezoelectric actuator 11 and rotary slider 12 are pressurized againsteach other by pressurized means 15. Applying a driving voltage toelectrodes of piezoelectric material 11 b through electric cable 16, thevibrator body 11 a vibrates and the rotary slider 12 is driven byfrictional force between actuator 11 and rotary slider 12. Internalcasing 1.2 is driven by the piezoelectric actuator. In the presentembodiment, the pressurized means 15 can be implemented by a coilspring, but it can also be a pressure plate, a wave washer spring, orlike pressing devices. The piezoelectric actuator 11 may, in someapplications, be exchanged for an electrostrictive actuator.

The position sensor 17 is attached to the surface of internal casing1.2. Rotary scale 18 is mechanically attached to the surface of therotary slider 12. Electric power supply to position sensor 17 anddetected signals thereof are transferred by electric cable 19. Positionsensor 17 detects relative rotational position by detecting the rotaryscale 18.

In the second rotary guide 2, the rotation drive unit 220 issubstantially similar to rotation drive unit 210. Rotation drive unit220 comprises a piezoelectric actuator 21, a rotary slider 22, a bearing23, a screw part 24, a pressurized means 25, a first electric cable 26,a position sensor 27, a rotary scale 28, a second electric cable 29, anexternal casing 2.1 and internal casing 2.2.

Structure of second rotary guide 2 is similar to first rotary guide 1. Astructural difference of second rotary guide 2 from first rotary guide 1is that the function of external casing 2.1 and internal casing 2.2 areinterchanged. The piezoelectric actuator 21 is supported through thepressurized means 25 to external casing 2.1. Position sensor 27 is alsofixed to external casing 2.1. Rotary slider 22 is fixed to internalcasing 2.2.

In the embodiment shown in FIG. 6A, only one position sensor and oneactuator for each of the guides 1 and 3 have been shown for the sake ofclarity in the illustration. The position sensors and actuators may beinstalled more than one to each of the guides. In this manner,additional position sensors and actuators can be provided to be used asbackup or supplemental to the first ones in various instances of theoperation of the manipulator to increase reliability, stability andprecision of the manipulator.

As in the first embodiment, the manipulator 200 of the second embodimentis constrained to operate needle positioning within a maximum availablespace [2] determined by the tilted arrangement of the second rotaryguide 3 with respect to the first rotary guide 1, as discussed inreference to FIGS. 4A and 4B. With such arrangement, as illustrated inFIG. 5B, the needle manipulator 200 is configured to position the needleat any position between a substantially perpendicular position (whereθ=0 degrees) and a maximum angle of inclination θ3 determined byequation (1).

<Available Exemplary Materials for Rotation Units 210 or 220>

Certain Available Exemplary Materials for rotation drive units 210 or220 may be selected, as follows:

Vibrator body: non-magnetic metal, ceramics (e.g., alumina, zirconia,partially stabilized zirconia), and other non-magnetic materials;

Rotary slider: engineering plastic material such aspolytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), polyimide(PI), Polyamide-imide (PAI), Polyphenylene sulfide (PPS), fiberreinforced plastic material such as carbon filled, glass fiber filled,or ceramics material;

Bearing: ceramics, plastic, air bearing;

Position sensor: optical-electrical type, fully optical (optical fiber);

Scale: print on plastic sheet, molded plastic, glass grating, etc.;

Position sensor and index scale may be implemented in various differentmanners. For example, it can be implemented by micro optical encoders.Alternatively, it can be implemented as a purely optical sensor, byusing optical fibers.

FIG. 6B illustrates a variation of the second embodiment where, in thefirst rotation drive unit 210, a light source fiber fs1 delivers lightto the rotary scale 18 and a collecting fiber fd1 is used to detectlight reflected from the rotary scale 18. Similarly, in the secondrotation drive unit 220, a light source fiber fs2 delivers light to therotary scale 28 and a collecting fiber fd2 is used to detect lightreflected from the rotary scale 28. The use of optical fibers may beparticularly desirable to avoid the use of electrical wiring forminimizing noise and interference in the MRI system, in particular toavoid interference with RF-pulse signals.

Advantageously, in the second embodiment, accurate positioning up to anorder of microns can be implemented by the use of optical rotaryposition sensors and piezoelectric actuators. Accurate positioning isavailable by piezoelectric actuator and feedback signaling, which can beautomated by controllers operated with programmed algorithms. At leasttwo piezoelectric vibrators and two position sensors are arranged intothe parts which are not relatively movable. Arranging the piezoelectricvibrators and position sensors within non-movable parts permits that allelectric cables can be tied into one bundle. Therefore, shielding ofelectric cables to decrease noises which MRI receives can be simplified.The manipulator can be moved without entangling of cables, soarrangement of electric cables can be simplified.

Conventionally, prior to every needle incision operation, the needleholder 6 and the base body 5 must be sterilized because they are touchedby clinician and patient. In accordance with embodiments disclosedherein, base body 5 and other parts fixed to external casing 1.1 can bemade of disposable and recyclable materials, such as plastic. In thismanner, these parts can be disposable in one clinical procedure. Theneedle holder 6 and the internal casing 2.2 can also be made ofdisposable materials. In this manner, the characteristics ofpiezoelectric actuators are stable because the friction surface of therotary slider which faces to piezoelectric vibrator is a new surface ineach clinical procedure.

Arranging piezoelectric actuators and rotary sliders to be ring or arcshape to be fit to the circular shape of rotary guides, the manipulatorcan be motorized to be automated, and yet maintain a small size. Holdingtorque of piezoelectric actuator stabilizes the manipulator in a stopstate. Alternatively, stop screws as those provided in the firstembodiment may be arranged within the external casing 1.1 so that aclinician may optionally secure the rotating guides with the screws, inaddition to the piezoelectric actuator stop. FIG. 7A illustrates anexample of a motorized manipulator 200, in accordance with amodification of the second embodiment. In FIG. 7A, set screws 201 and203 are used as a locking mechanism for locking the rotational guides 1and 3, respectively, in a stopped position. Stop set screws can beadvantageous in a case where there is possibility of unexpected rotatingforce being applied to the rotary guides, while the piezoelectricactuator keep its stopped position only by friction, for example.

FIG. 7B illustrates a further modification to the needle manipulator 200in accordance with the second embodiment. In FIG. 7B, the base body 5includes a fitting and sliding portion 5 a in which the first rotaryguide 1 is disposed (fitted) with a certain degree of tolerance, suchthat the first rotary guide 1 slides in a vertical direction Vperpendicular to the bottom surface of base body 5. When the firstrotary guide 1 is allowed to slide in the vertical direction V(perpendicularly) with respect to the bottom surface of base body 5, adistance h (height) between the bottom surface of the base body 5 andthe first rotary guide 1 can be selectively adjusted. Once the rotaryguide 1 is located at a desired distance or height h with respect to thebottom surface of base body 5, the first rotary guide 1 is locked inplace by a height locking mechanism, such as a set screw 51. In thismanner, it is possible to adjust the position (height or distance) ofthe crossing point 9 with respect to a target surface (e.g., the skin 8of a patient's body). In this embodiment, even when the position(height) of crossing point 9 is changed along the axis 1 a of the firstrotary guide 1, the rotational axis 1 a of the first rotary guide 1, therotational axis 3 a of the second rotary guide 3, and the needle holderaxis 6 a still cross each other at a single crossing point 9.Advantageously, the crossing point 9 can be adjusted to the targetsurface to, for example, accommodate the various shapes of a patient'sbody parts. In this embodiment, it should be noted, that when the rotaryguide 3 is made to slide vertically with respect to the base body 5, theset screw 201 will also slide in the V direction together with therotary guide 1. To that end, the sliding portion 5 a of base body 5should be modified to include a hollow portion 5 b to allow verticaldisplacement of the set screw 201.

<Third Embodiment>

A third embodiment is now described with respect to FIGS. 8A, 8B and 9.A needle manipulator 300, in accordance with the third embodiment issubstantially similar to the manipulator 100 of the first embodiment inthat needle positioning is effected by manually rotating the rotaryguides 1 and 3. A notable difference in the third embodiment, incontrast to the first one, is that the manipulator 300 includes anattached RF-coil.

Specifically, FIG. 8A is a perspective view of manipulator 300 and FIG.8B is a perspective view of the manipulator 300 showing a vertical cutalong plane H-H, in accordance with third embodiment. FIG. 9A is asectional view of the manipulator 300 cut along the vertical plane H-H,according to the third embodiment. The needle manipulator 300 of thepresent embodiment may be particularly suitable for use in MRI-guidedpercutaneous interventions. In this embodiment, the manipulator 300includes attachments for an RF-coil which is used in a MRI-scanner. Thestructure for positioning needle 7 is basically the same as the onedescribed in first embodiment.

As illustrated in FIG. 8A, the manipulator 300 includes a firstattachment 30 and a second attachment 31 to fix the manipulator 300 to asingle loop RF-coil 32. The first attachment 30 is placed directly on apatient such that a bottom surface of the first attachment 30 rests onthe patient's skin, for example. The needle manipulator 300 includes aplurality of fiducial markers 10 a, 10 b, 10 c and 10 d in the firstrotary guide 1 and fiducial markers 10 e, 10 f, 10 g through 10 h (10 enot shown) on the second rotary guide 3, as described in the firstembodiment. In addition, at least the first attachment 30 includesfiducial markers 33 a, 33 b, 33 c and 33 d (markers 33 c and 33 d arenot seen in FIG. 8A). Since the first attachment 30 remains fixed to thebody of the subject under examination, the fiducial markers 33 a-33 dserve as a reference, so that needle position and orientation can betracked with fiducial markers located on either one or both of theguides (e.g., fiducial markers 10 a-10 h).

FIG. 8B illustrates a perspective view of the manipulator 300 mountedonto RF-coil 32 in which a sectional cut along vertical plane H-H isperformed. FIG. 9A illustrates a sectional view of the needle placementmanipulator cut along a vertical plane H-H, according to the thirdembodiment. The first attachment 30 includes a flat setting portion onwhich the RF-coil 32 is set, and a circular projection portion 30 aconfigured to engage with the second attachment 31. Similarly, thesecond attachment 31 includes a flat setting portion below which theRF-coil is set, and a circular projection portion 31 a which engageswith the projection portion 30 a of the first attachment 30.

As illustrated in FIG. 9A, the single loop RF-coil 32 is placed with thecircular projection 30 a of attachment 30 going through the opening ofthe RF-coil 32. The second attachment 31 is fixed to the base body 5 andthe circular projection section 31 a is disposed at the bottom surfacethereof. These two attachments 30 and 31 are configured to be engaged(fitted) by the two circular projections 30 a and 31 a, respectively,such that the two attachments remain fixed at relative positions whilesecuring the RF-coil 32 therebetween. Fixing the two attachments 30 and31 at relative positions can be done by one or more set screws (notshown), or by force fitting (pressure), or by one or more air chucks(not shown), or by any other mechanical means that will preventunexpected movement or dislodging between the two attachments.

FIG. 9B illustrates a detailed view of section A shown in FIG. 9A wherea first attachment 30 engages with a second attachment 31 on an outersurface thereof. FIG. 9C illustrates a detailed view of section A shownin FIG. 9A where a first attachment 30 engages with a second attachment31 on an inner surface thereof. Regardless of how the two attachmentshave been joined, the two attachments 30 and 31 are engaged (fitted)into each other by the two circular projections 30 a and 31 a,respectively, such that the two attachments remain fixed at relativepositions while securing the RF-coil 32 therebetween. Notably, as shownin FIGS. 9B and 9C, the second attachment 31 may be integrated into thebase body 5. In this manner, the base body 5 and the second attachment31 are integrally attached as a single mechanical structure. Moreover,the second attachment 31, the based body 5 and the non-movable portionof the first guide 1 can be integrally formed as a single mechanicalstructure. Making the second attachment 31 an integral part of base body5, or making the second attachment 31 with base body 5 and part of thefirst guide 1 an integral structure may facilitate prompt attachment anddetachment of the needle manipulator 300 onto the RF-coil 32. However,as described above, the attachment 31 may be removably attached to thebase body 5.

Once the two attachments are assembled with the manipulator 300, theaxis 1 a of the first rotary guide 1, the axis 3 a of the second rotaryguide 3 and the needle holder axis 6 a of the needle holder 6 arearranged to cross at a single crossing point 9. The crossing point 9 ispreferably located at the center of gravity of manipulator 300, whichshould be located at the geometric center of the bottom surface of firstattachment 30. Fitting part of circular projections 31 a and 30 a can bereplaced by screw adjustment, so that the crossing point 9 is adjustablewith respect to the patient's skin, as shown in FIG. 7B.

If the RF-Coil includes a plurality of openings, like a body matrixcoil, the RF-coil attachment 30 is prepared according to the shape ofeach opening. If the opening of the RF-coil is of a square shape,attachment 30 should be made in a square shape too, and attachment 31should be made to adapt, on one side, to the shape of the base body 5,and on the other side to the attachment 30.

Turning now to FIGS. 10A through 10C, a description is provided of anexemplary procedure for attaching and detaching the manipulator 300 andRF-coil 32 onto a body of a target patient. FIG. 10A shows a firstattachment 1001 with an upward protruding ring (protrusion section), asingle loop RF-coil 1002, and a second attachment 1003 with a downwardprotruding ring. In FIG. 10A, the first attachment 1001 with itsprotruding ring facing upward is first set on a patient (the subject ofneedle placement), and the second attachment 1003 with the protrudingring facing downward is attached to base body 5 of the needlemanipulator. The protruding ring of first attachment 1001 is arranged toengage with the protruding ring of the second attachment 1003. In FIG.10B, the RF-coil 1002 is set on the first attachment 1001. The openingof RF-coil 1002 is loosely fit around the protruding ring of the firstattachment 1001, so that the RF-coil 1002 can be rotated or moved toadjust the positioning of cabling and other parts (not shown in thefigure). In FIG. 10C, the needle manipulator unit is set onto the firstattachment 1001. The second attachment 1003, which is the partprotruding downward from the needle manipulator unit, engages firmlywith the first attachment 1001 so that needle position and orientationwith respect to the patient can be accurately known, by tracking thefiducial markers. FIG. 11 is a perspective view of the assembled needlemanipulator attached to the RF-coil 1002 and the first and secondattachments 1001 and 1003.

Certain Advantages in the third embodiment are that the opening ofRF-coil and the manipulator's opening (space through which the needle isinserted) are made to coincide with each other. In this manner, theopening can be advantageously utilized for a clinician's access to entrypoint (incision point) of a patient's skin. The RF-coil 32 andmanipulator 300 are removably combined into one unit, so that clinicalprocedure could be simple.

<Fourth Embodiment>

A fourth embodiment is now described with respect to FIG. 12. A needlemanipulator 400, in accordance with the fourth embodiment issubstantially similar to the manipulator 200 described above inreference to the second embodiment. A notable difference in the fourthembodiment is that the needle manipulator 400 includes motorizedrotational guides 1 and 3, and an attached to RF-coil 32.

Needle positioning in the manipulator 400 of the forth embodiment isautomated with piezoelectric actuators and optical sensors. In thepresent embodiment, a second attachment 31 and the base body 5 can becombined into a single body.

In this manner, RF-Coil's opening and manipulator's opening are made tocoincide with each other and utilized for clinician's access to entrypoint of patient's skin. The positioning accuracy of the manipulatorwith respect to the subject of the needle placement is improved bydirectly positioning the first attachment to the patient and thecapability of attaching the manipulator to the first attachment withhigh repeatability. The piezoelectric actuator can guarantee precisepositioning and steady fixation (stop); this prevents movement of themanipulator 400 even when movement of the patient occurs. In addition,in an automated robotic application, the actuators can be controlled bya controller (CPU) with programmed algorithms designed so that automaticposition adjustment occurs in response to patient movement.

<Fifth Embodiment>

FIG. 13 illustrates block diagram of an automated image-guided needlepositioning system 500 which includes a motorized manipulator, and canbe programmed for automatic (e.g., remote or robotic) manipulation, inaccordance with a fifth embodiment. FIG. 13 is a block diagram of theimage-guided needle positioning system 500. In accordance with presentembodiment, the block diagram shows a function performed by each blockincluded in the system 500. Each function may be implemented purely inhardware and/or a combination of software and hardware.

An image guided needle positioning system 500 includes namely thefollowing main functional blocks: a needle placement manipulator 510, anMRI-system 520, image guide system 530, a manipulator controller 540,and an actuator controller 550. All of the functional blocks areinterconnected by circuit or network connectivity. Some of the blocksmay be integrated into a single block provided that he combined blockstill performs the functionally of each block. The needle placementmanipulator 510 corresponds to any of the first or second embodimentsdisclosed herein, as long as an actuator 512 and a sensor 514 can beimplemented within the manipulator. The needle placement manipulator 510including the RF coil 516 corresponds to any of the third and fourthembodiments disclosed herein.

The MRI guide system 530 includes an image monitor (image display) 531,an input device module 532 (e.g., keyboard, mouse, touchpad, etc.), acentral processing unit (CPU) implemented by one or moremicroprocessors, hardware memory 534 (volatile and non-volatile memoryand storage devices, such a hard drives may be included), and an ImageGuide Software module 535. The image guide software module 535 includes,among other things, programmed algorithms to communicate and controleach of the other functional blocks. An example of such image guidedapplication is described by Song et al., in a non-patent literaturearticle entitled “Biopsy Needle Artifact Localization in MRI-guidedRobotic Transrectal Prostate Intervention,” IEEE transactions onBiomedical Engineering, July 2012.

Image guide system 530 acquires images of a target patient or body-partthereof, of the fiducial markers of in manipulator and RF-coil base(see, e.g., FIG. 8A), and of the needle 7. The manipulator controller540 communicates with actuator controller 550 for needle positioning.Actuator controller 550 drives piezoelectric actuator 512 or USM(ultrasonic) motor and controls the driving with position sensor 514 inclosed-loop control. Kinematics calculator 542 translates the signalsfrom the image guide system 530 into control signals for the actuatorcontroller 550. Actuator controller 550 is implemented in hardware forcontrolling an actuator (e.g., piezoelectric actuator or USM motor).Position controller 552 may be implemented in software and/or hardware.The position controller 552 calculates a control amount for the actuator512 so that the needle moves in a target orientation angle based onsignal output from a position sensor 514.

In the case of operating under the magnetic field of an MR-basedmodality (MRI system 520), the static magnetic field magnet 522generates a static magnetic field in the imaging space. The gradientcoil 524 generates a gradient magnetic field in the X-axis direction, agradient magnetic field in the Y-axis direction and a gradient magneticfield in the Z-axis direction in the imaging space.

An RF transmitter 526 outputs RF pulses (RF current pulses) to the RFcoil 516. The RF coil 516 transmits the RF pulses to the human body. TheRF coil receives an MR signal generated due to excited nuclear spininside the human body according to the RF pulse. An RF receiver 528detects the MR signal. Then, the detected data or a signal based on thedetected data is input into an image guide system 530. Volumetric MRIscans can confirm the position and orientation of the needle's tip,based on fixed reference fiducials (e.g., disposed on the RF-coilattachments) and movable fiducials disposed on at least one of therotary guides. Forward Kinematic Mapping (FKM) can be implemented in theposition controller 552 to iteratively drive the needle to a desiredtarget position and to even compensate for positional errors. It isenvisioned, for example, an arrangement where, for every needleincision, the position of the manipulator and patient can be registeredwith respect to the coordinates of the MRI system. During a needleincision procedure, the position of the tip of the needle is alsoregistered with respect to the manipulator, the patient and the MRIsystem. Then a forward kinematic algorithm performs calculations forcontrolling the manipulator and updating the position and orientation ofthe tip of the needle. To ensure precision of needle placement, a safetyroutine that continuously compensates for needle artifacts can be addedto the algorithm.

<Other Embodiments and Modifications>

In the embodiments disclosed above, various combinations andmodifications will be readily evident to persons having ordinary skillin the art. As discussed above with respect to FIGS. 4A and 4B, forexample, the needle manipulator may be modified to include a secondrotary guide 3 having a diameter larger than a diameter of the firstrotary guide 1. This modification can allow for the second rotary guide3 to be placed outside of the first rotary guide 1 instead of inside, asshown in all of the first to fourth embodiments. In addition, althoughthe third to fifth embodiments are directed to MRI-based image guidedneedle manipulators, the needle manipulators disclosed herein may beapplicable to other imaging modalities, such as ultrasound, mammography,computed tomography (CT) and the like. When applied to other modalities,the fiducial markers need not be readable by MRI-scanners as disclosedabove. Instead, the fiduciary markers can be modified to conform to thespecific imaging modality, or can be removed.

In each of the first to fourth embodiments, the first rotary guide 1 issupported by the base body 5 and connects to a first rotation body 2.The second rotary guide 3 is supported by the first rotation body 2 at aslated angle with respect to the first rotary guide 1. The firstrotation body 2 may be of a fixed height it can change in height, suchthat the second rotary guide 3 can be positioned from substantiallyparallel to substantially perpendicular to the first rotary guide 1. Inthis manner, positioning of a needle by the needle holder 6 can apply toother than the maximum angle of rotation and optimal rotation spacediscussed above.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

What is claimed is:
 1. A needle placement manipulator comprising: aneedle holder which holds a needle along an axis of the needle holder; aring-shaped rotatable guide configured to support the needle holder andto position the axis of the needle holder to a direction of insertionsuch that the axis of the needle holder passes through an insertionpoint on a subject of needle placement; a base body on which thering-shaped rotatable guide is supported; a first attachment including abase surface and a setting portion on which an RF-coil is set; and asecond attachment connected to the base body and including an attachingportion which attaches the second attachment to the first attachment,wherein the base surface of the first attachment is configured to be theclosest plane of the needle placement manipulator to the subject ofneedle placement, wherein the ring-shaped rotatable guide is slanted andnot parallel with respect to the base body such that the axis of theneedle holder intersects a rotation axis of the ring-shaped rotatableguide at a remote center of motion, and wherein, during needleplacement, the ring-shaped rotatable guide rotates to move the needleholder along a circular path around a cone of acceptance such that theaxis of the needle holder, the apex of the cone of acceptance, and therotation axis of the ring-shaped rotatable guide constantly intersecteach other at the remote center of motion even when the direction ofinsertion changes during rotation of the ring-shaped rotatable guide. 2.The needle placement manipulator according to claim 1, wherein the firstattachment and the second attachment have an opening region around theaxis of the needle holder.
 3. The needle placement manipulator accordingto claim 1, wherein the ring-shaped rotatable guide is a rotary guidewhich has a circular opening concentric with its rotation axis, and thecircular opening extends to the setting portion on which the RF-coil isset.
 4. The needle placement manipulator according to claim 1, furthercomprising at least one position sensor arranged in the ring-shapedrotatable guide, wherein the at least one position sensor detects arotational position of the ring-shaped rotatable guide.
 5. A needleplacement manipulator according to claim 1, wherein the setting portionof the first attachment includes a projection portion which is formedaccording to a shape of an opening of the RF-coil, and the secondattachment is attached rigidly to the projection portion.
 6. The needleplacement manipulator according to claim 1, wherein the ring-shapedrotatable guide has a circular opening concentric with the rotation axisof the ring-shaped rotatable guide, wherein the ring-shaped rotatableguide includes an outer part and an inner part, the inner part beingmovable relative to the outer part, wherein the outer part is attachedto the base body and the needle holder is attached to the inner part,and wherein, during needle placement, the inner part rotates to move theneedle holder along the circular path inside the circular opening. 7.The needle placement manipulator according to claim 1, wherein thering-shaped rotatable guide is slanted at a fixed angle with respect tothe base body, and wherein, during needle placement, the ring-shapedrotatable guide rotates to move the needle holder along the circularpath around the cone of acceptance without changing the fixed angle. 8.The needle placement manipulator according to claim 1, wherein thering-shaped rotatable guide includes a first rotary guide and a secondrotary guide which are slanted with respect to each other such thattheir respective rotation axes cross at a first angle with respect toeach other, and wherein the first rotary guide is attached to the basebody, and the needle holder is attached to the second rotary guide. 9.The needle placement manipulator according to claim 8, furthercomprising one or more pillars connecting the first rotary guide to thesecond rotary guide such that the second rotary guide is slanted withrespect to the first rotary guide.
 10. The needle placement manipulatoraccording to claim 1, wherein the ring-shaped rotatable guide includes afirst rotary guide supported by the base body and a second rotary guidearranged inside or outside of the first rotary guide, and wherein thesecond rotary guide is arranged at an angle with respect to the firstrotary guide such that, during needle placement on the subject, thefirst rotary guide and a part of the second rotary guide are maintainedon a single plane parallel to the base surface of the first attachment.11. The needle placement manipulator according to claim 10, wherein,during needle placement, the second rotary guide rotates the needleholder along the base of the cone of acceptance in a circular path, andthe first rotary guide rotates the second rotary guide such that therotation axis of the second rotary guide precesses around the cone ofacceptance, and the rotation axis of the first rotary guide, therotation axis of the second rotary guide, and the axis of the needleholder cross each other at the insertion point.
 12. The needle placementmanipulator according to claim 1, wherein the ring-shaped rotatableguide includes a first rotary guide and a second rotary guide slantedwith respect to each other such that their respective rotation axes arefixed at a first angle with respect to each other.
 13. The needleplacement manipulator according to claim 12, wherein the rotation axisof the second rotary guide and the axis of the needle holder are fixedat a second angle with respect to each other, wherein the second angleis greater than or equal to the first angle, and wherein the followingcondition is satisfiedθ1+θ2 ≤θ3 =π/2−tan⁻¹(T/R), where θ1 is the first angle, θ2 is the secondangle, θ3 is a maximum angle of inclination of the axis of the needleholder with respect to the rotation axis of the first rotary guide, andT is a height from a contact surface of the base body to an uppersurface of the first rotary guide and R is the radius of the firstrotary guide.
 14. The needle placement manipulator according to claim12, wherein the rotation axis of the first rotary guide, the rotationaxis of the second rotary guide, and the axis of the needle holder crosseach other at a crossing point located at or above the insertion point.15. The needle placement manipulator according to claim 14, wherein thecrossing point is on the plane of the base surface of the firstattachment.
 16. The needle placement manipulator according to claim 1,further comprising at least one actuator arranged in the ring-shapedrotatable guide, wherein the at least one actuator moves the ring-shapedrotatable guide so as to displace the needle holder around the base ofthe cone of acceptance for needle placement.
 17. The needle placementmanipulator according to claim 16, wherein the actuator includes aslider part which is pressurized to a friction element fixed topiezoelectric material by pressurized means, and the slider part isactuated by the vibration of a vibrator.
 18. The needle placementmanipulator according to claim 16, wherein the actuator includespiezoelectric material.
 19. The needle placement manipulator accordingto claim 18, wherein the actuator includes a vibrator body to which thepiezoelectric material is fixed and a slider part which is pressurizedto the vibrator body by pressurized means and actuated by the vibrationof the vibrator body.
 20. The needle placement manipulator according toclaim 19, wherein the vibrator body is made of ceramic material.
 21. Theneedle placement manipulator according to claim 17, wherein the frictionelement includes resin material.
 22. The needle placement manipulatoraccording to claim 17, wherein the slider part includes resin material.23. A needle placement manipulator comprising: a needle holderconfigured to hold a needle; a ring-shaped rotary guide systemconfigured to hold the needle holder and to position the needle holderto a direction of insertion with respect to a subject of needleplacement; and an attachment including an attaching portion to which thering-shaped rotary guide system is attached and a setting portion onwhich an RF-coil is set, wherein a base surface of the setting portionis configured to be disposed on the subject, wherein the ring-shapedrotary guide system is slanted and not parallel with respect to theattaching portion such that the axis of the needle holder intersects arotation axis of the ring-shaped rotary guide system at a remote centerof motion, and wherein, during needle placement, ring-shaped rotaryguide system is configured to move the needle holder along a circularpath around the base of a cone of acceptance such that the axis of theneedle holder, the apex of the cone of acceptance, and the rotation axisof the ring-shaped rotary guide system constantly intersect each otherat the remote center of motion even when the direction of insertionchanges during rotation of the ring-shaped rotary guide system.
 24. Theneedle placement manipulator according to claim 23, wherein thering-shaped rotatable guide is slanted at a fixed angle with respect tothe attaching portion, and wherein, during needle placement, thering-shaped rotatable guide rotates to move the needle holder along thecircular path around the cone of acceptance without changing the fixedangle.
 25. The needle placement manipulator according to claim 23,wherein the ring-shaped rotary guide system includes a first rotaryguide supported by the attaching portion and a second rotary guidearranged inside or outside of the first rotary guide, and wherein thesecond rotary guide is arranged at an angle with respect to the firstrotary guide such that, during needle placement on the subject, thefirst rotary guide and a part of the second rotary guide are maintainedon a single plane parallel to the base surface of the setting portion.26. The needle placement manipulator according to claim 25, wherein,during needle placement, the second rotary guide rotates the needleholder along the base of the cone of acceptance in a circular path, andthe first rotary guide rotates the second rotary guide such that therotation axis of the second rotary guide precesses around the cone ofacceptance, and the rotation axis of the first rotary guide, therotation axis of the second rotary guide, and the axis of the needleholder cross each other at the insertion point.
 27. The needle placementmanipulator according to claim 23, wherein the remote center of motionis located at the base surface of the setting portion or on a planeparallel to the base surface.
 28. The needle placement manipulatoraccording to claim 27, further comprising a distance adjustmentmechanism configured to adjust the plane on which the remote center ofmotion is located.
 29. The needle placement manipulator according toclaim 28, wherein the distance adjustment mechanism varies a distancefrom the base surface of the setting portion to the remote center ofmotion such that the remote center of motion is located at a planeparallel to the base surface above the base surface or below the basesurface.
 30. The needle placement manipulator according to claim 23,wherein the ring-shaped rotary guide system includes a first rotaryguide and a second rotary guide which are slanted with respect to eachother such that their respective rotation axes cross at a first anglewith respect to each other.
 31. The needle placement manipulatoraccording to claim 30, wherein the second rotary guide rotates at aslated angle with respect to the first rotary guide.
 32. The needleplacement manipulator according to claim 30, wherein the rotation axisof the first rotary guide, the rotation axis of the second rotary guide,and the axis of the needle holder cross each other at the remote centerof motion.